Regional Anatomy of the Pelvis and Perineum

Question 1

Boundaries and anatomical relationships of subdivisions of pelvis & associated viscera

Answer 1

• Bony pelvis
  
  • Innominate bones (ileum, ischium, pubis)
  • Sacrum and coccyx
• Pelvic inlet
  
  • From sacral promontory to pubic symphysis
• Pelvic outlet
  
  • From pubic symphysis to coccyx
  • Following ischiopubic ramus, ischial tuberosity, and sacrotuberous ligament
• False (greater) pelvis
  
  • Superior to pelvic inlet
  • Part of abdominal cavity
• True (lesser) pelvis
  
  • From pelvic inlet to pelvic outlet (at pelvic diaphragm)
  • Pelvic cavity (contains pelvic viscera)
  • Pelvic walls consist of bone, ligaments (sacrospinous and sacrotuberous), and muscles (piriformis, obturator internus, with fascia)
  • Pelvic floor consists of pelvic diaphragm (levator ani muscles, coccygeus muscles with superior and inferior fascia covering muscles)

Question 2

Pelvic diaphragm

Answer 2

• Levator ani muscle
• Coccygeus muscle
• Fascia:
  
  • Superior
  • Inferior

Question 3

Internal pelvic viscera: rectum

Answer 3

• Supported by and passes through muscular portion of pelvic diaphragm
• Diaphragm forms a sling, when contracted, aids external and internal anal sphincters in controlling defecation
• Pelvic diaphragm supports rectum and pelvic viscera

Question 4

Urogenital diaphragm

Answer 4

• Deep transverse perineus muscles in deep perineal pouch
• Superior fascia
• Inferior fascia (perineal membrane)
  
  • Platform for the external genitalia

Question 5

Perineum

Answer 5

• Diamond shaped region between abducted thigh
• Inferior to pelvic diaphragm

Question 6

Anatomical relationships between uterus, ovaries, subdivisions of broad ligament

Answer 6

• Ovaries
  
  • Produce eggs
  • Endocrine organ
• Uterine (fallopian) tubes
  
  • Fimbriae: collect ovulated egg
  • Infundibulum
  • Ampulla: normal site of fertilization
  • Isthmus
• Uterus
  
  • Fundus
  • Body
  • Cervix: projects into upper end of vagina

Question 7

Ligaments of female internal reproductive organs

Answer 7

• Broad ligament: peritoneal fold
  
  • Mesovarium:
    
    • Supports ovary and surrounds suspensory and ovarian ligaments and vessels
  • Mesosalpinx:
    
    • Surrounds and supports uterine tubes
  • Mesometrium:
    
    • Broad ligament inferior to mesosalpinx surrounding uterine vessels
• Cardinal ligaments
  
  • Located at base of mesometrium, extending from cervix to pelvic wall

Question 8

Testes

Answer 8

• Produce spermatozoa in seminiferous tubules
• Endocrine organ
• Rete testis
  
  • Collecting chamber for spermatozoa
• Efferent ductules
  
  • Connects rete testis with epididymis

Question 9

Epididymis

Answer 9

• Stores and functions in maturation of spermatozoa
• Head
• Body
• Tail
  
  • Continuous with ductus deferens

Question 10

Ductus deferens & ejaculatory ducts

Answer 10

• Ductus deferens
  
  • Muscular (smooth muscle) tube that transports spermatozoa from epididymis to ejaculatory ducts
• Ejaculatory ducts
  
  • Combined ducts of ampulla (ductus deferens) and seminal vesicle
  • Empties into prostatic urethra

Question 11

Seminal vesicles and prostate

Answer 11

• Seminal vesicle
  
  • Contributes secretions to semen
• Prostate
  
  • 30-40 individual glands
  • Individual ducts drain into prostatic urethra
  • Contributes secretions to semen

Question 12

Innervation of perineum

Answer 12

• Genitofemoral nerve
• Ilioinguinal nerve
• Pudendal nerve
• Posterior femoral cutaneous nerve

Question 13

Boundaries and contents of superficial and deep perineal pouches

Answer 13

• Superficial pouch
  
  • From superficial perineal fascia (Colle’s fascia) to perineal membrane
  • Encloses erectile tissues and their muscles
• Deep pouch
  
  • From perineal membrane to superior fascia of urogenital diaphragm
  • Encloses deep transverse perineus muscle and urethral sphincter (skeletal muscles)

Question 14

Areas of the pelvic bones most commonly fractured & clinical implications of the pubo-obturator fracture

Answer 14

• Pubic rami
  
  • At risk during AP compression of pelvis (crush accident, heavy object fall)
  • High risk of complication due to damage to urinary bladder and urethra
  • Straddle injury (fracture of all 4 pubic rami) –> serious loss of pelvic stability
• Acetabulum
  
  • At risk during fall on the feet from height
  • Forces from ground drive head of femur into acetabulum
  • Lateral compression of pelvis places acetabula and iliac blades at risk

Question 15

Most common injuries to the pelvic floor during childbirth

Answer 15

• Tearing injuries
  
  • Grade 1 = superficial tissues
  • Grade 2 = some tearing of muscles
  • Grade 3 = tear extends to anal sphincter
• Grade 2+ tears most commonly pubococcygeous and puborectalis parts of levator ani
• Episiotomy (intentional cut) intends to decrease traumatic tearing of perineum
  
  • Typically not performed anymore
  • May be employed in cases of fetal distress, if descent of fetus becomes arrested, or when delivery with assistance of instruments is planned

Question 16

BPH and urinary implications

Answer 16

• Common after middle age - undergoes hormone-induced hypertrophy
• Especially marked in middle lobe area between urethra and ejaculatory ducts
• Enlarging prostate projects into bladder - distorts and compresses prostatic urethra
  
  • Impedes urination
  • May cause nocturia, dysuria, and/or urgency
  • Increases risk of bladder infxns
• Prostate can be palpated via DRE
  
  • Close relationship to anterior wall of rectum + full bladder –> makes gland more easily palpable
• Part or all of prostate may be surgically removed
  
  • Newer approach passes through urethra

Question 17

Anatomic etiology & clinical implications of testicular torsion and varicocele

Answer 17

• Testicular torsion
  
  • Spermatic cord becomes twisted, usually just superior to upper pole of testis
  • Most commonly linked to congenital malformation of processus vaginalis
  • Obstructs venous drainage –> edema –> blocks arterial supply to testis –> avascular necrosis of testis
• Varicocele of testis (“bag of worms” scrotum)
  
  • Abnormal enlargements of pampiniform plexus of veins in spermatic cord
  • Caused by incompetent/absent valves within testicular veins –> pooling of blood or backflow
  • L-sided varicocele more common
  • Present in 10-15% of males